It is known to provide multi-hulled marine vessels with suspension between at least two hulls and the body of the vessel as disclosed in the Applicant's International Patent Application Publication Numbers WO2004/016497, WO2011/143692, WO2011/143694 and WO2013/181699, incorporated herein by reference, which disclose various configurations of multi-hulled vessels having a body portion at least partially supported on at least four support points above at least two hulls. It has been found in vessels having one left hull and one right hull which provide the primary source of roll stability, that when the longitudinal distribution of roll forces (or the Roll Moment Distribution—RMD) is designed to suit the loads on the at least four support points when the vessel is stationary or operating in buoyancy mode, the suspension system can exhibit signs of an imbalance in the longitudinal distribution of roll forces during operation in other modes such as semi-planing or planing.